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rfc:rfc8354

Internet Engineering Task Force (IETF) J. Brzozowski Request for Comments: 8354 J. Leddy Category: Informational Comcast ISSN: 2070-1721 C. Filsfils

                                                      R. Maglione, Ed.
                                                           M. Townsley
                                                         Cisco Systems
                                                            March 2018
  Use Cases for IPv6 Source Packet Routing in Networking (SPRING)

Abstract

 The Source Packet Routing in Networking (SPRING) architecture
 describes how Segment Routing can be used to steer packets through an
 IPv6 or MPLS network using the source routing paradigm.  This
 document illustrates some use cases for Segment Routing in an
 IPv6-only environment.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are candidates for any level of Internet
 Standard; see Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc8354.

Brzozowski, et al. Informational [Page 1] RFC 8354 Use Cases for IPv6 SPRING March 2018

Copyright Notice

 Copyright (c) 2018 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (https://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
 2.  IPv6 SPRING Use Cases . . . . . . . . . . . . . . . . . . . .   3
   2.1.  SPRING in the Small Office  . . . . . . . . . . . . . . .   3
   2.2.  SPRING in the Access Network  . . . . . . . . . . . . . .   4
   2.3.  SPRING in Data Center . . . . . . . . . . . . . . . . . .   5
   2.4.  SPRING in Content Delivery Networks . . . . . . . . . . .   5
   2.5.  SPRING in Core Networks . . . . . . . . . . . . . . . . .   6
 3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
 4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
 5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
   5.2.  Informative References  . . . . . . . . . . . . . . . . .   7
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
 Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

Brzozowski, et al. Informational [Page 2] RFC 8354 Use Cases for IPv6 SPRING March 2018

1. Introduction

 Source Packet Routing in Networking (SPRING) architecture leverages
 the source routing paradigm.  An ingress node steers a packet by
 including a controlled set of instructions, called segments, in the
 SPRING header.  The SPRING architecture is described in
 [SEGMENT-ROUTING].  This document illustrates some use cases for
 SPRING / Segment Routing in an IPv6-only environment.

2. IPv6 SPRING Use Cases

 The use cases described in this section do not constitute an
 exhaustive list of all the possible scenarios: this section only
 includes some of the most common envisioned deployment models for
 Segment Routing over IPv6 (SRv6).
 In addition to the use cases described in this document, all the
 SPRING use cases [RFC7855] are also applicable to the SRv6 data
 plane.

2.1. SPRING in the Small Office

 An IPv6-enabled Small Office, Home Office (SOHO) provides ample
 globally routed IP addresses for all devices in the SOHO.  An IPv6
 small office with multiple egress points and associated provider-
 assigned prefixes will, in turn, provide multiple IPv6 addresses to
 hosts.  A small office performing source and destination routing
 [PA-MULTIHOMING] will ensure that packets exit the SOHO at the
 appropriate egress based on the associated delegated prefix for that
 link.
 A SPRING-enabled SOHO provides the ability to steer traffic into a
 specific path from end hosts in the SOHO or from a customer edge
 router in the SOHO.  If the selection of the source-routed path is
 enabled at the customer edge router, that router is responsible for
 classifying traffic and steering it into the correct path.  If hosts
 in the SOHO have explicit source selection rules, classification can
 be based on the source address or associated network egress point,
 thus avoiding the need for implicit classification techniques based
 on Deep Packet Inspection (DPI).  If the traffic is steered into a
 specific path by the host itself, it is important to know which
 networks can interpret the SPRING header.  This information can be
 provided as part of the host configuration as a property of the
 configured IP address.

Brzozowski, et al. Informational [Page 3] RFC 8354 Use Cases for IPv6 SPRING March 2018

 The ability to steer traffic to an appropriate egress or utilize a
 specific type of media (e.g., low power, Wi-Fi, wired, femtocell,
 Bluetooth, Multimedia over Coax Alliance (MoCA), HomePlug, etc.)
 within the home itself are obvious cases that may be of interest to
 an application running within a SOHO.
 Steering to a specific egress point may be useful for a number of
 scenarios, including:
 o  regulatory compliance;
 o  performance of a particular service associated with a particular
    link;
 o  cost imposed due to data caps or per-byte charges;
 o  distinguishing between personal vs. work traffic in homes with one
    or more teleworkers; and
 o  provision of specific services by one ISP vs. another.
 Information included in the SPRING header, whether imposed by the end
 host itself, a customer edge router, or within the access network of
 the ISP, may be of use at the far ends of the data communication as
 well.  For example, an application running on an end host with
 application support in a data center can utilize the SPRING header as
 a channel to include information that affects its treatment within
 the data center itself, which allows for application-level steering
 and load balancing without relying upon implicit application-
 classification techniques at the edge of the data center.  Further,
 as more and more application traffic is encrypted, the ability to
 extract (and include in the SPRING header) just enough information to
 enable the network and data center to load balance and steer traffic
 appropriately becomes more and more important.

2.2. SPRING in the Access Network

 Access networks deliver a variety of types of traffic from the
 service provider's network to the home environment and from the home
 towards the service provider's network.
 For bandwidth management or related purposes, the service provider
 may want to associate certain types of traffic to specific physical
 or logical downstream capacity pipes.
 This mapping is not the same thing as classification and scheduling.
 In the cable access network, these pipes are represented at the Data-
 Over-Cable Service Interface Specification [DOCSIS] layer as

Brzozowski, et al. Informational [Page 4] RFC 8354 Use Cases for IPv6 SPRING March 2018

 different service flows, which are better identified as distinct data
 links.  As such, creating this separation allows an operator to
 differentiate between different types of content and perform a
 variety of differing functions on these pipes, such as byte capping,
 regulatory compliance functions, and billing.
 In a cable operator's environment, these downstream pipes could be a
 DOCSIS [DOCSIS] service flow, a service group, or a specific
 Quadrature Amplitude Modulation (QAM) as in Annex B of [ITU.J83].
 Similarly, the operator may want to map traffic from the home sent
 towards the service provider's network to specific upstream capacity
 pipes.  Information carried in a packet's SPRING header could provide
 the target pipe for this specific packet.  The access device would
 not need to know specific details about the packet to perform this
 mapping; instead, the access device would only need to know the
 interpretation of the SPRING header and how to map it to the target
 pipe.

2.3. SPRING in Data Center

 Some data center operators are transitioning their data center
 infrastructure from IPv4 to native IPv6 only, in order to cope with
 IPv4 address depletion and to achieve larger scale.  In such an
 environment, source routing (as enabled by SRv6) can be used to steer
 traffic across specific paths through the network.  The specific path
 may also include a given function that one or more nodes in the path
 are requested to perform.
 Additionally, one of the fundamental requirements for data center
 architecture is to provide scalable, isolated tenant networks.  In
 such scenarios, Segment Routing can be used to build a construct to
 steer the traffic across that specific path and to identify specific
 nodes, tenants, and functions.

2.4. SPRING in Content Delivery Networks

 The rise of online video applications and new, video-capable IP
 devices has led to an explosion of video traffic traversing network
 operator infrastructures.  In the drive to reduce the capital and
 operational impact of the massive influx of online video traffic, as
 well as to extend traditional TV services to new devices and screens,
 network operators are increasingly turning to Content Delivery
 Networks (CDNs).
 Several studies showed the benefits of connecting caches in a
 hierarchical structure following the hierarchical nature of the
 Internet.  In a cache hierarchy, one cache establishes peering

Brzozowski, et al. Informational [Page 5] RFC 8354 Use Cases for IPv6 SPRING March 2018

 relationships with its neighbor caches.  There are two types of
 relationships: parent and sibling.  A parent cache is essentially one
 level up in a cache hierarchy.  A sibling cache is on the same level.
 Multiple levels of hierarchy are commonly used in order to build an
 efficient cache architecture.
 In an environment where each single cache system can be uniquely
 identified by its own IPv6 address, a list containing a sequence of
 the caches in a hierarchy can be built.  At each node (cache) in the
 list, the presence of the requested content is checked.  If the
 requested content is found at the cache (a cache hits scenario), the
 sequence ends even if there are more nodes in the list; otherwise,
 the next element in the list (the next node/cache) is examined.

2.5. SPRING in Core Networks

 While the overall amount of traffic offered to the network continues
 to grow, and considering that multiple types of traffic with
 different characteristics and requirements are quickly converging
 over a single network architecture, the network operators are
 starting to face new challenges.
 Some operators are currently building, or plan to build in the near
 future, an IPv6-only native infrastructure for their core network.
 These operators are also looking at the possibility to set up an
 explicit path based on the IPv6 source address for specific types of
 traffic in order to efficiently use their network infrastructure.  In
 the case of IPv6, some operators are currently assigning or plan to
 assign IPv6 prefix(es) to their IPv6 customers based on regions/
 geography, thus the subscriber's IPv6 prefix could be used to
 identify the region where the customer is located.  In such an
 environment, the IPv6 source address could be used by the edge nodes
 of the network to steer traffic and forward it through a specific
 path other than the optimal path.
 The need to set up a source-based path that goes through some
 specific middle/intermediate points in the network may be related to
 different requirements:
 o  The operator may want to be able to use some high-bandwidth links
    for a specific type of traffic (like video) and thus avoid the
    need for overdimensioning all the links of the network;
 o  The operator may want to be able to set up a specific path for
    delay-sensitive applications;

Brzozowski, et al. Informational [Page 6] RFC 8354 Use Cases for IPv6 SPRING March 2018

 o  The operator may have the need to be able to select one (or
    multiple) specific exit point(s) at peering points when different
    peering points are available;
 o  The operator may have the need to be able to set up a source-based
    path for specific services in order to be able to reach some
    servers hosted in some facilities that are not always reachable
    through the optimal path; or
 o  The operator may need to be able to provision guaranteed disjoint
    paths (a so-called "dual-plane network") for diversity purposes.
 All these scenarios would require a form of traffic engineering
 capabilities in an IPv6-only network environment.

3. IANA Considerations

 This document has no IANA actions.

4. Security Considerations

 This document presents use cases to be considered by the SPRING
 architecture and potential IPv6 extensions.  As such, it does not
 introduce any security considerations.  However, there are a number
 of security concerns with source routing at the IP layer [RFC5095].
 It is expected that any solution that addresses these use cases also
 addresses any security concerns.

5. References

5.1. Normative References

 [RFC7855]  Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
            Litkowski, S., Horneffer, M., and R. Shakir, "Source
            Packet Routing in Networking (SPRING) Problem Statement
            and Requirements", RFC 7855, DOI 10.17487/RFC7855,
            May 2016, <https://www.rfc-editor.org/info/rfc7855>.

5.2. Informative References

 [DOCSIS]   CableLabs, "New Generation of DOCSIS Technology", October
            2013, <http://www.cablelabs.com/news/
            new-generation-of-docsis-technology/>.
 [ITU.J83]  ITU-T, "Digital multi-programme systems for television,
            sound and data services or cable distribution", ITU-T
            Recommendation J.83, December 2007,
            <https://www.itu.int/rec/T-REC-J.83/en>.

Brzozowski, et al. Informational [Page 7] RFC 8354 Use Cases for IPv6 SPRING March 2018

 [PA-MULTIHOMING]
            Baker, F., Bowers, C., and J. Linkova, "Enterprise
            Multihoming using Provider-Assigned Addresses without
            Network Prefix Translation: Requirements and Solution",
            Work in Progress, draft-ietf-rtgwg-enterprise-pa-
            multihoming-03, February 2018.
 [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
            of Type 0 Routing Headers in IPv6", RFC 5095,
            DOI 10.17487/RFC5095, December 2007,
            <https://www.rfc-editor.org/info/rfc5095>.
 [SEGMENT-ROUTING]
            Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
            Litkowski, S., and R. Shakir, "Segment Routing
            Architecture", Work in Progress, draft-ietf-spring-
            segment-routing-15, January 2018.

Acknowledgements

 The authors would like to thank Brian Field, Robert Raszuk, Wes
 George, Eric Vyncke, Fred Baker, John G. Scudder, Adrian Farrel,
 Alvaro Retana, Bruno Decraene, and Yakov Rekhter for their valuable
 comments and inputs to this document.

Contributors

 Many people contributed to this document.  The authors of this
 document would like to thank and recognize them and their
 contributions.  These contributors provided invaluable concepts and
 content for this document's creation.
 Ida Leung
 Independent
 Email: ida@brumund.ca
 Stefano Previdi
 Cisco Systems
 Via Del Serafico, 200
 Rome  00142
 Italy
 Email: stefano@previdi.net
 Christian Martin
 Arista Networks
 Email: cmartin@arista.com

Brzozowski, et al. Informational [Page 8] RFC 8354 Use Cases for IPv6 SPRING March 2018

Authors' Addresses

 John Brzozowski
 Comcast
 Email: john_brzozowski@cable.comcast.com
 John Leddy
 Comcast
 Email: John_Leddy@cable.comcast.com
 Clarence Filsfils
 Cisco Systems
 Brussels
 Belgium
 Email: cfilsfil@cisco.com
 Roberta Maglione (editor)
 Cisco Systems
 Via Torri Bianche 8
 Vimercate  20871
 Italy
 Email: robmgl@cisco.com
 Mark Townsley
 Cisco Systems
 Email: townsley@cisco.com

Brzozowski, et al. Informational [Page 9]

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